1. Field of the Invention
The invention is concerned with joints formed between tubing and metallic members made of machined metal of substantially full density such as flanges and more particularly is concerned with joints of increased torque resistance between tubing and metallic members and with a unique and novel process for producing such an improved torque resistant joint.
2. Prior Art
The prior art teaches any number of tubing-flange joints. A number of such joints are obtainable wherein the flange has a circular cross section hole therethrough adapted to receive an end of the tube, the hole having at least one annular channel extending therefrom into the flange, by placing an end of the tube within the hole, the end having an external diameter very nearly equal to the diameter of the hole and the tube being formulated of a less hard metal than the flange, and forcing an expanding means into the end of the tube and thereby forming a force-fit joint between the exterior of the tube and the hole through the flange. Other joints have been made by flaring tube ends and clamping, bolting or otherwise pressing a mating portion of a metallic member thereagainst.
Generally the prior art flanges have been formulated by machining from metal of a desired hardness, for example, of hardness Rockwell B90 (Hardness as referred to herein is as measured by ASTM E 18). Such joints occasionally have developed leaks due to lack of a sufficient resistance of the joint to torque which is encountered in many every day operations using said joints. For example, when said joints are part of the hydraulic system of heavy earth moving equipment they are often subjected to sharp torque strains which cause the joints to break loose thus leading to leaking about the joints.
In the past it has been standard practice to clean metal oxide coatings which may have been formed on the tubing mating portion of the metallic member off of said mating portion in the belief that a stronger more torque resistant and more leak proof joint would thereby result. This has been particularly true with iron based alloys to insure the removal of rust (Fe.sub.2 O.sub. 3).
The present invention provides an improved tube-machined metallic member joint of significantly higher resistance to torque than prior art joints through a relatively inexpensive treatment of the metallic member part of the joint prior to the formation of the joint. Surprisingly, while the treatment does not cause any measurable change in hardness of the machined metallic members, it still leads to joints of significantly increased torque resistance. Also provided by the present invention is a process for forming a more torque resistant joint through a specific treatment of the machined metallic member portion thereof prior to the formation of the joint.